The present invention relates to an improvement in front-rotary working machines.
Among popular walking-type working machines are cultivators which, though rotations of cultivating claws mounted on a cultivating shaft assembly, not only cultivate the ground but also travel in a direction instructed by a human operator; such machines are commonly called xe2x80x9cfront-tine working machinesxe2x80x9d. In recent years, development of so-called xe2x80x9cfront-rotary working machinesxe2x80x9d has been proceeding, which are walking-type working machines that include cultivating claws in front of a machine body having transporting wheels mounted thereon. Such front-rotary working machines can readily cultivate on machine-turning areas (also known as butts) of a field because the cultivating claws are disposed in front of the machine body, and achieve superior operability because the human operator can operate the machine while looking ahead. Because of these advantages, the front-rotary working machines have been attracting people""s attention.
Note that the xe2x80x9cmachine-turning areasxe2x80x9d or xe2x80x9cbuttsxe2x80x9d are dead or temporarily uncultivated areas that are produced at opposite ends of a field by temporary stoppage of cultivating operations due to U-turn motions of the working machine, for example, in a case where the machine cultivates the field while reciprocating parallel to one side of the field.
Among examples of such front-rotary working machines is an xe2x80x9cAgricultural Working Machinexe2x80x9d disclosed in Japanese Patent Publication No. 3,015,821. The disclosed agricultural working machine (hereinafter also referred to as a conventional front-rotary working machine) is of a so-called xe2x80x9cdown-cutxe2x80x9d type which is designed to cultivate the ground by rotating the cultivating shaft assembly, and hence the cultivating claws, downwardly to the ground and which is used primarily for plowing. The conventional front-rotary working machine will be outlined below.
FIG. 16 is a schematic view of the conventional front-rotary working machine. The conventional front-rotary working machine 200 is a walking-type cultivator which includes an engine 201 mounted on a machine body 202, and a power transmission casing 203 provided beneath the machine body 202. The power transmission casing 203 includes a rear transmission case 204 and front rotary case 205 that are formed as a one-piece or integral unit. A pair of left and right transporting wheels 207 are mounted at both ends of an axle 206 projecting from opposite sides of a rear portion of the transmission case 204, and a rotary-side intermediate shaft 208 is disposed on a front portion of the rear transmission case 204. The conventional front-rotary working machine also includes a cultivating shaft assembly 209 having a plurality of cultivating claws 210 provided thereon. Within the front rotary case 205, an endless chain 213 is wound on and extends between a driving sprocket 211 mounted on the rotary-side intermediate shaft 208 and a driven sprocket 212 mounted on the cultivating shaft assembly 209.
The engine 201 employed in the conventional front-rotary working machine 200 is a horizontal engine having an output shaft 214 projecting laterally outwardly therefrom. With a belt 218 wound on and extending between a driving pulley 215 mounted on the output shaft 214 and a driven pulley 217 mounted on an input shaft 216 projecting sideways from the transmission case 204, output power of the engine 201 can be transmitted to the transmission system. Namely, a belt transmission mechanism 221 for transmitting the power from the engine 201 to the transmission system is composed of the driving pulley 215 mounted on the output shaft 214 extending horizontally widthwise of the machine 200, driven pulley 217 mounted on the input shaft 216 also extending horizontally widthwise of the machine 200 and belt 218 wound on the driving pulley 215 and driven pulley 217. The belt transmission mechanism 221 can be activated or deactivated via a tension roller 219 functioning as a main clutch mechanism. Namely, power transmission by the belt transmission mechanism 221 can be enabled by tightening the belt 218 via the tension roller 219 and disabled by loosening the belt 218. Thus, with the output power of the engine 201, not only the left and right transporting wheels 207 can be driven via the axle 206, but also the cultivating claws 210 can be driven by way of the rotary-side intermediate shaft 208, chain 207 and cultivating shaft assembly 209. Further, in FIG. 16, reference numeral 220 represents a handle.
Furthermore, in the front-rotary working machine 200, four rows of the cultivating claws 210 are disposed in the widthwise direction of the machine body 202 (i.e., in a direction intersecting the sheet of FIG. 16). The working machine 200 can cultivate the ground by all the cultivating claws 210 rotating in a predetermined one direction together with the cultivating shaft assembly 209.
In the above-discussed front-rotary working machine 200, the rear transmission case 204 and front rotary case 205 of the power transmission casing 203 are integrally combined into a generally L shape (or vertically-inverted V shape) as viewed sideways. Namely, the rear transmission case 204 is inclined rearwardly downwardly while the front rotary case 205 is inclined forwardly downwardly.
As the cultivating claws 210 (constituting a rotary working unit of the working machine 200) cultivates the soil Gr21, the cultivated soil Gr22 tends to heap on the ground. The thus-heaped soil Gr22 may hit the bottom of the rear transmission case 204. As the cultivating depth of the cultivating claws 210 increases, the height of the rear transmission case 204 above the ground surface tends to decrease; if such a tendency becomes strong, the cultivated soil Gr22 would be shaved or pushed away by the bottom of the transmission case 204, which often results in an unsmooth, uneven cultivated ground surface. Because of such unsatisfactory cultivating performance or finish, the conventional front-rotary working machine 200 is susceptible of (i.e., has room for) improvement.
Further, because the rear transmission case 204 is tilted rearwardly downwardly as mentioned above, it can become an obstacle to the cultivated soil Gr22, in which case the cultivated soil Gr22 may pile up in front of the transmission case 204. If the transmission case 204 runs on the piled-up soil Gr23, the soil Gr23 can become a great resistance to travel of the front-rotary working machine 200. The traveling resistance presented by the piled-up soil Gr23 is usually unbalanced, and thus if the traveling resistance is great, it would impose great loads on the human operator to keep linear traveling performance of the working machine 200; in this regard too, the conventional front-rotary working machine 200 has room for improvement.
Furthermore, in the conventional front-rotary working machine 200, where the horizontal engine 201 is employed, the belt transmission mechanism 221 is disposed to the right side of the horizontal engine 201, and the left and right transporting wheels 207 are disposed outwardly of the opposite sides of the belt transmission mechanism 221. Therefore, a distance between the left and right transporting wheels 207 unavoidably becomes great, which would result in a great overall width of the working machine 200.
Often, cultivating operations on a field include weeding operations (furrow-to-furrow tillage) for removing weeds from between ridges (i.e., furrows) in addition to ordinary cultivating operations for cultivating the ridges. Because the furrows between the ridges usually have small widths, there are limitations to the weeding operations using the working machine 200 of a great overall width.
In view of the foregoing prior art problems, it is a first object of the present invention to provide a front-rotary working machine of a type including cultivating claws in front of a machine body with transporting wheels mounted thereon which can achieve a satisfactory cultivating finish by minimizing interference, of a transmission case, with soil cultivated by a rotary working unit and significantly lessen loads on a human operator by suppressing traveling resistance presented by cultivated soil.
It is a second object of the present invention to provide a front-rotary working machine including cultivating claws in front of a machine body with transporting wheels mounted thereon which can achieve enhanced operability in cultivating furrows.
To accomplish the above-mentioned first object, the present invention provides an improved front-rotary working machine which comprises a transmission case provided beneath an engine, front and rear driving shafts operatively connected to the engine and projecting from front and rear portions, respectively, of the transmission case so that transporting wheels are drivable via the rear driving shaft and a rotary working unit is drivable via the front driving shaft, where the transmission case has a generally flat underside to extend substantially parallel to a ground surface to be cultivated.
Even when soil cultivated by the rotary working unit has heaped to a considerable height on the ground surface, the front-rotary working machine of the present invention can prevent the transmission case from undesirably interfering with the heaped soil; namely, it is possible to avoid the prior art problem that the heaped soil is undesirably shaved by the underside of the transmission case. As a result, the front-rotary working machine of the present invention can ensure a superior cultivating finish.
Further, with the present invention, the cultivated soil can be reliably prevented from piling up in front of the transmission case. Thus, it is always possible to prevent the transmission case from running on piled-up soil, so that resistance to travel of the working machine can be minimized. Because unbalanced traveling resistance can be thus avoided, it is possible to effectively lessen loads on a human operator in keeping desired linear traveling performance.
In a preferred embodiment, the underside of the transmission case is slightly inclined rearwardly and downwardly with respect to the ground surface to be cultivated. Because the underside of the transmission case is flat and inclined in the rearward and downward direction with respect to the ground surface to be cultivated, the working machine can appropriately level the cultivated soil with the underside of the transmission case, thereby achieving an enhanced the cultivating finish. Besides, because the underside of the transmission case is generally parallel to the ground surface and slightly inclined in the rearward and downward direction, the working machine can readily get over cultivated soil when the transmission touches cultivated and piled-up soil.
In order to accomplish the above-mentioned second object, the present invention provides an improved front-rotary working machine which comprises: a vertical engine having an output shaft projecting downward from a body of the engine; a transmission case provided beneath the vertical engine and thereby having a relatively great dimension in a front-and-rear direction of the working machine and a relatively small dimension in a widthwise direction of the working machine; left and right transporting wheels connected to both end portions of an axle or driving shaft projecting laterally from opposite sides of a rear end portion of the transmission case; and a rotary working unit disposed in front of the transmission case. By the use of the vertical engine with its output shaft projecting downward, the overall width of the working machine can be significantly reduced. Further, because the transmission case is disposed beneath the vertical engine, a power transmission mechanism for transmitting power from the engine to a transmission system does not project in the widthwise direction of the working machine. Further, because the transmission case has a greater dimension in the front-and-rear direction of the working machine and a smaller dimension in the widthwise direction of the working machine than those in the conventional counterparts, the overall width of the working machine can be reduced even further. These arrangements allow the distance between the left and right transporting wheels, connected to the axle at a rear end portion of the transmission case, to be reduced as necessary, as a result of which the overall width of the front-rotary working machine can be reduced. Consequently, the working machine can be readily positioned on a narrow furrow between ridges of a field to thereby efficiently work on the narrow furrow while traveling therealong, and thus it is possible to enhance the operability of the working machine in narrow-space operations, such as weeding operations on a furrow.